Cathode-ray signal-generating tube



Evian? R. c. HERGENRQTHER 2,192,73

I CATHODE-HAY SIGNAL-GENERATING TUBE Filad Aug. 30, 1937 TELEVISION TRANSMITTWG APPQRATUS PZCTU'RE FREQUENCY GENERATGQ Ll N E FREQUENCY GENERATOR ATTORN EY Patented Mar. 212, 3

Rndoli c. net-ceaseless, nccclnst, Long isle it. 522, assignor to meltlne Qorporation, a coraeration cs Delaware connection linguist so, lost, serial No. lenses 2 (cl. Edd -1 .53)

This invention relates to cathode-ray time syscircuit separate from the target shucture and tems and, more particularly, to cathode-ray siasecond anode, but not undesirably affected by nal-genera lng tubes useful in television transother elements or circuits of the system.

mitting systems, In accordance with the present invention, a

Various types of cathode-ray signal-generating c y al-gcneratmg ube c p ses on Q tubes have heretofore been developed and, inelectron gun for developing, accelerating, and general, they have comprised an elongated evacllfocusing an electron beam, a second anode and a atcd envelope including, at one end, a. plurality photosensitive target in the path of the beam. of electrodes, conventionally referred to as on n Ou pu electl'fllie 15 P d electrically 119 electron gun, which serve to develop, accelerate, connected to the second anode through any low and focus an electron beam. a photosensitive mpedance path and having an area of the same target is disposed in the opposite end of the en order of magnitude as that of the second anode. velope in the path of the beam. The target The output electrode is displaced from the secgenerally comprises a dielectric sheet, such as nd amide s d i lt 0 t e ectron beam mica, with a continuous metallic conductive coatand in juxtap s to the t e Collecting 5 mg or signal plate on one sid thereof d electrons emitted by the target and there is prophotosensitive mosaic coating on the other side v ded means for pp y opemting Pfltentlals o providing, in enact, minute condensers having the electrodes of the tube, the output electrode the continuous metallic coating as a common be p d to e a ed at p e t al n; electrode, Images of scenes to be transmitted positive relative to the second 211110618a With this are projected on the mosaic of the target and a m t a vid -fr q y m d a n v ltthe beam is so deflected as to scan successive age y be ol od in t e Output it'which frames or series of parallel lines on the target. is n01? undlisimbly afi d y Scanning 0 Ot er The projection of the image on the target causes elements of the System ill - photoelectron emission by the mosaic elements, better understanding of ve tio 25 proportional to the light intensity at correspondtogether wi other and further Objects t e e ing elements of the image and th l g b reference is had to the following description during the scanning operation, efiects secondary taken in connection with the accompanying dra electron emission by the mosaic elements varying s, a d its s ope w be po ted out in the onw in accordance withtheir photoelectron on. p n 1- 39 These electrical efiects are utilized to develop The single Ls? e or the drawins is a schemati a correspondingly varying modulation voltage in diagram of a complete television transmitting the output circuit of the tube including the target sy m in l in a athode-ray si nol-senerat- 1 signal plate. I ing tube embodying the present invention.

Ordinarily, secondary and pnotoelect Referring now more particularly to the drawemitted from the target are collected by the elecs. the t vi t an t n syst m illustrated trade of the gun havi th t; punitive t t includes a conventional camera or projector Hi tial, commonly called the second anode, and the and a tube s tube compl'lses signal plate of the target is used as an output an elongated envelope it? including a cy indrical electrode, a suitable load circuit being connected end s or e it and a nlar d spherical w thereto. It has been found that certain. adend portion In t e end p rtion 58 there is vantages could be obtained by the second difipflsefl cethflde a control i a cus anode as the output electrode but, in such an e or fi anode and a second anode 26, in arrangement, the proximity and consequent dose the order named, these electrodes constituting coupling of t electrode and t 3mg what is conventionally referred to in the art as (w ments of the tube would result in undesirable rean electron The second time it erab y action efiects between the signal-output voltage comprises a lic or ting on the inner and the scanning fields. V surface of the envelope, as shown. A ph0tosensi 1 It is an object of the present invention to protlve target it is disposed in the sp e ca nd norvide an improved cathode-ray signal-generating M n 2653 of the envelope. The target may be con- 69 do scrihed which includes an output electrode and stance, such silverwatube characterized by simplicity of structure and .structed in the conventional manner and include reliability and eiflciency in operation. a t sheet of dielectric, such as mica, having a It is a iurther object oi the invention to .pro=- metallic rear coating or sig al plate and a photovide a cathode-ray tube of the character de sensitive mosaic "e of suitable subhint-oxygen mixture electrons emitted by the photosensitive surface of the target. This electrode is disposed at an intermediate position in the envelope, displaced from the second anode 24, outside of the path of the beam, and in juxtaposition to the target. The electrode 26 may, similarly to the anode 24,

comprise a metallic film orcoating on the innersurface of the portion 20 of the envelope l8.

Suitable operating potentials are supplied to the several electrodes of the tube I I from a voltage divider 21 connected to a suitable source, indicated as plus and minus, and grounded at an intermediate point, as shown. The output circuit includes a load resistor 28 connected at one end to the output electrode 26 and at its other end to a point on the voltage divider such that the potential applied to the output electrode is positive relative to that applied to the second anode.

There are also provided lineand frame-ire quency scanning generators l2 and I3 having their output circuits connected to deflecting coils I4 and I5, respectively, of the tube II. The output circuit of the tube including resistor 28 is connected to conventional television transmitting apparatus, indicated generally at I6 and terminating in an antenna H.

The apparatus just described, in general, represents a conventional television transmitting system. The construction and operation of such apparatus being well known in the art, a detailed description thereof is unnecessary herein. In brief, however, in the operation of the apparatus described, images of the scene to be transmitted are projected by the camera I0 on the mosaic surface of the target 25, effecting photo electron emission by the variousmosaic elements in accordance with the light intensity at the corresponding elements of the images. Electrons are generated, acceleratecband developed into a beam by the electron gun 2l2 l, the beam being focused on the target 25 and causing secondary electron emission by the mosaic elements. Currents of saw-toothed wave form generated by the generators l2 and I3 are passed through the scanning coils I4 and I5, respectively, thereby producing magnetic fields which deflect the beam horizontally and vertically, causing it to scan frames or series of parallel lines on the target in the usual manner. There is thereby developed in the output circuit of the tube including the output electrode 26 a video-frequency voltage which is proportional to the variations in light and shade in the image of the scene to be transmitted. This voltage is utilized in the transmitter apparatus l6 to modulate a carrier'wave which isbroadcast from the'antenna I! in the usual manner.

By virtue of the size of the output electrode 26, its proximity to the target 25 and the potential applied thereto, a substantial part of both the primary and secondary elecrodes emitted from the target are collected by this electrode, causing a current to flow in the output circuit and a resultant voltage to be developed across the resistor 28 which are dependent upon the variations in illumination of the elements of the image projected on the mosaic. At the same time, by virtue of the location of the output electrode 26, there is a minimum interaction between the signals developed in its circuit and the periodic fluctuations impressed on the electrodes 2l-24 of the electron gun and the scanning coils l4 and i5.

While there has been described what is at present considered to be the preferred embodiment of this invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention, and it'is, therefore, aimed in the appended claims to cover all such changes 'and modifications as fall within the true spirit and scope of the invention.

What is claimed is:

l; A cathode-ray signal-generating tube comprising an electron gun for developing, accelerating, and focusing an electron beam and including a second anode, a photo-sensitive target in the path of said beam, an output electrode electrically unconnected to said second anode through any low impedance path and having an area of the same order of magnitude as that of said second anode, displaced from said second prising an elongated evacuated envelope, an electron gun disposed in one end of said envelope for developing, accelerating, and focusing an electron beam and including a second anode, a photosensitive target disposed in the other end of said envelope in the path of said beam and adapted to have an image of a scene projected thereon, and an output electrode electrically unconnected to said second anode through any low impedance path and having an area of the same order of magnitude as that of said second anode, disposed at an intermediate position in said envelope displaced from said gun, outside the path of said beam, and in juxtaposition to said target, for collecting electrons emitted by said target, and means for applying operating potentials to the electrodes of said tube, said output electrode being adapted to be maintained at a potential positive relative to said second anode.

RUDOLF C. HERGENROTHER. 

